I) On Fig. 1, draw a graph of extension against load for a spring which obeys Hooke’s law. [1] extension 0 load Fig

 
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6
 
Fig. 3.1 shows a skier taking part in a downhill race.
Fig. 3.1
(a) 
The mass of the skier, including his equipment, is 75 kg. In the ski race, the total vertical
change in height is 880 m.
Calculate the decrease in the gravitational potential energy (g.p.e.) of the skier.
decrease in g.p.e. = ...........................................................[2]
(b) 
The skier starts from rest. The total distance travelled by the skier during the descent is
2800 m. The average resistive force on the skier is 220 N.
Calculate
(i) 
the work done against the resistive force,
work done = ...........................................................[2]
(ii) 
the kinetic energy of the skier as he crosses the finishing line at the end of the race.
kinetic energy = ...........................................................[2]
(c) 
Suggest why the skier bends his body as shown in Fig. 3.1.
...............................................................................................................................................[1]
[Total: 7]

 
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